Slab position alarm



DCC 6, 1955 A. W. BEHN ET AL SLAB POSITION ALARM Filed NOV. 2l, 1952 JNVENTORS United States Patent SLAB PosrrroN ALARM Albert W. Behn and Clarence C. Cobb, Beaumont, Tex.,

assiguors to Socony-Vacuum Oil Company Incorporated, New York, N. Y., a corporation of New York Application November 21, 1952, Serial No. 321,883 4 claims. (ci. 340-259) This invention relates to a device for determining proper positioning of a plurality of solid objects, such as slabs or cakes of petroleum wax, at a predetermined time. The mechanism was specifically designed for and is particularly well adapted for usein connection with a continuous machine for molding petroleum wax cakes. In that embodiment, the present invention is used to detect discharge of wax cakes from molding pans in order to avoid the diiculties arising when a full pan is returned to the stage at which molten wax is charged into the pans.

The invention contemplates an alarm which will detect the presence of a predetermined number of slabs, cakes or the like in a predetermined position at a predetermined time. Upon failure of the desired number of'objects to be present in the desired place at the desired placefand time, the combination hereinafter described is adapted to halt operation of a controlled mechanism or sound an alarm, preferably both.

The continuous wax slabbing machine with which the present invention has been used is described and claimed in copending application Serial Number.254,682, filed November 3, 1951, by Leon H. Jennings. In that con tinuous machine, a plurality of pans are carried by chain conveyors past a filling stage in which a desired quantity of molten Wax is discharged into each of the pans. The pans thereafter pass through a cooling chamber wherein the wax solidies to slabs of the desired size and shape. Thereafter the pans are inverted on a steel table and discharged onto a conveyor belt to be carried to a packaging station.

In the event the wax slab fails to drop from any of the pans, the lled pan or pans pass again into the filling station and a further quantity of molten wax is discharged into one or more pans which are already full. Such action naturally results in the flow of molten wax over the edge of the pan and upon the operating parts of the slabbing machine, fouling the machine and wasting product.

`It is the principal object of the present invention to determine whether each of the pans has been properly emptied and, in the event of failure to dump any pan, the controlled slabbing machine is shut down and an alarm signal is given. In its broader aspects, the' invention is applicable to other installations wherein it is necessary to detect the presence or absence of a solid cake or the like at a desired time and place.

Other objects and advantages of the invention will be apparent from the annexed drawings wherein Figure l is an elevation in partial section of the discharge station of a wax slabbing machine showing cakes being discharged from one set of pans;

Figure 2 is a plan view in partial section of the cake discharge station;

Figure 3 is a fragmentary detail View taken from the under-side of one slab detector with its associated mechanical linkage and switch; and

Figure 4 is a diagrammatic sketch of the electric circuits involved, together with the alarm and slabbing machine control operated thereby.

Referring now to Figure 1, a plurality of molding pans 10 are carried between conveyor chains 11 above a steel table 12. The pans 10 are inverted above the table 12 and, in normal operation, the wax cake is essentially free of its pan 10 but is propelled thereby while sliding along the table 12. At the discharge edge of the table 12 is a cross conveyor belt 13, operated intermittently by a drive not shown to remove the cakes discharged from each series of pans. In the embodiment shown, four pans are carried abreast between the conveyor chains 11 and four cakes will normally be discharged at a time from the pans onto the cross conveyor 13. It will be recognized that the invention contemplates and is readily adaptable to any desired number of pans in each row.

Figure l shows how each cake 14 will drop onto the cross conveyor 13 as it passes over the discharge edge of table 12. As the conveyor chains 11 move farther to the right in Figure 1, carrying the pans 10 with them, the cake 14 is pushed olf the edge of table 12 and drops onto the cross conveyor 13 thereby being brought in contact with a knob 15 extending from a switch housing 16 mounted under the discharge edge of table 12.

As will be noted from Figure 2, there are four knobs 15, one for each of the cakes to be discharged from a single row of pans 10. As these cakes fall to position on the cross conveyor 13, they force the corresponding knobs 15 back into the switch housing 16, thus actuating the electrical control circuits hereinafter described.

The detailed linkages within the switch housing 16 are shown in Figure 3. Each knob 15 is carried on a lever 17, pivoted at 18 to the switch housing and riding on a guide rod 19.v A spring 2i) exerts mild pressure to maintain the knob 15 in its most extended position when not in contact with a wax cake 14.

Associated with each of the levers 17 is a double throw switch 21 which is preferably of the microswitch type requiring only slight movement to actuate its contact points. In the embodiment shown, a spring leaf 22, pivoted at one end to the lever 17 and at its other end to the housing of switch 21 bears on the pin 23 actuating the switch contacts. Suitable electrical connections for each switch 21 are brought together in a cable 24 passing through the switch housing 16.

The manner in which the foregoing elements co-act to control the wax slabbing machine is shown diagrammatically in Figure 4. The switches 21 appear in Figure 4 within the rectangle set ofI by broken lines representing the switch housing 16. Current is supplied for operation of the controls from any suitable source such as a normal 11,0 volt A. C. line. The switches 21 are shown in normal position when no wax slabs are present on the cross conveyor 13. At the time a wax slab falls to the cross conveyor 13, it actuates the corresponding switch 21, closing the circuit to light a signal lamp 25 associated with each of the switches 21. Illumination of the lamp 25 indicates that the corresponding wax cake has fallen into its proper place on the cross conveyor 13. Timed with operation of the wax slabbing machine is a cam 26 which acts to close a switch 27 at a time when the wax cakes should properly be in position on cross conveyor 13 and before the cross conveyor 13 has been set in motion to remove the wax cakes from the discharge station. In the event any wax cake has failed to fall into proper position on cross conveyor 13, the corresponding switch 21 will be in position to form a closed circuit including the relay 28, thus closing contacts A and B of that relay. Contact A of relay 28 is in series through normally closed contact C of relay 29 with an alarm klaxon 30 and a solenoid valve control 31. As shown, klaxon 30 and control 31 are in parallel with each other and this parallel arrangement is preferred. Sounding of klaxon 30 warns the operator that there has been a failure of at least one of the pans 10 to discharge properly and he may determine which pan has failed to empty by observing the lights 25. Thus lights 25 corresponding to properly discharged cakes will be lighted but there will be no illumination of the signal lamp 25 corresponding to a cake position in which a cake has not been properly discharged. The solenoid valve control 31 opens valve 32 in a compressed air line to air cylinder 33, causing the piston of the air cylinder 33 to move to the left thus operating clutch lever 34 through the agency of piston rod 35. Clutch lever 34 opens clutch 36 on the main drive shaft of the wax slabbing machine indicated at 37. The machine thus comes to a stop with the signal lamps for properly discharged cakes alight, enabling the operator to readily determine the position of the trouble and act to correct it.

The operator will rst press reset button 38, closing a circuit through normally closed contact D of relay 29, the coil of relay 29 and contact B of relay 28 which became closed at the time the alarm was given. Actuation of relay 29 opens contact C of that relay thus breaking the circuit which includes the klaxon 30 and solenoid. valve control 31. The operator is thus not annoyed by sounding of the alarm while clearing the machine and the air cylinder is released so that clutch 36 may be again engaged by manual operation of lever 34 when the operator is again ready to start the machine. The relay 29 closes contact E of that relay to establish a holding circuit through relay 29. After clearing the trouble, the operator engages clutch 36 and places the machine in operation with all controls ready for operation. It will be noted that the electrical control circuits shown in Figure 4 do not become again operative until cam switch 27 opens, thus causing relay 28 to be de-energized opening contacts A and B. The opening of contact B de-energizes relay 29 which is thereby returned to normal position.

We claim:

1. In a machine for preparing and discharging solid cakes as successive groups each containing a plurality of simultaneously discharged cakes, a control system actuated by failure to discharge an individual cake of one of said groups comprising a plurality of mechanical contact elements at the discharge station of said machine each projecting into the space occupied by one of said cakes of a group at discharge, a double throw switch arranged for actuation by each of said contact elements, a lamp circuit including the normally open contact of each of said switches, a iirst relay circuit including in parallel all the normally closed contacts of said switches, a normally open contact in said first relay circuit, mechanical means operated by said machine to close said last named contact at the time of discharge of one of said groups, an alarm circuit including a normally open contact and a normally closed contact, a lirst relay in said rst relay circuit adapted to close said open contact in said alarm circuit, a second relay circuit including a normally open contact, means for manually closing said last named Contact and a second relay in said second relay circuit adapted to open said normally closed contact in said alarm circuit.

2. In combination, a plurality of double throw switches biased to normally closed positions in parallel, an equal number of lamp circuits each including the normally open contact of one of said switches, a first relay circuit including all the normally closed parallel contacts of said switches, a normally open contact in said first relay circuit, means to periodically close said last named contact, an alarm circuit including a normally open contact and a normally closed contact, a first relay in said first relay circuit adapted to close said open contact in said alarm circuit, a second relay circuit including a normally open contact, manually operable means for closing said last named contact. and a second relay in said second relay circuit adapted to open said normally closed contact in said alarm circuit.

3. ln a machine for preparing and discharging solid cakes as successive groups each containing a plurality of simultaneously discharged cakes, a control system actuated by failure to discharge an individual cake of one of said groupsv comprising a plurality of mechanical contact elements at the discharge station of said machine each projecting into the space occupied by one of said cakes of a group at discharge, a double throw switch arranged for actuation by each of said contact elements, an indicator circuit including the normally open contact of each of said switches, a first relay circuit including in parallel all the normally closed contacts of said switches, a normally open contact in said first relay circuit, mechanical means operated by said machine to close said last named contact at the time of discharge of one of said groups, an alarm circuit including a normally open contact and a normally closed contact, a first relay in said first relay circuit adapted to close said open contact in said alarm circuit, a second relay circuit including a normally open contact, means for manually closing said last named contact and a second relay in said second relay circuit adapted to open said normally closed contact in said alarm circuit.

4. In combination, a plurality of double throw switches biased to normally closed positions in parallel, an equal number of indicator circuits each including the normally open contact of one of said switches, a first relay circuit including all the normally closed parallel contacts of said switches, a normally open contact in said first relay circuit, means to periodically close said last named contact, an alarm circuit including a normally open contact and a normally closed contact, a rst relay in said first relay circuit adapted to close said open contact in said alarm circuit, a second relay circuit including a normally open contact, manually operable means for closing said last named contact and a second relay in said second relay circuit adapted to open said normally closed contact in said alarm circuit.

References Cited in the ile of this patent UNITED STATES PATENTS 2,238,980 Metcalf Apr. 22, 1941 2,242,189 Zelov May 13,1941 2,317,839 Westin Apr. 27, 1943 2,523,184 Beall Sept. 19,1950 2,609,433 Goff Sept. 2,1952 2,617,972 Nutter Nov. 11,1952 

